Process and system for making artificial snow

ABSTRACT

Water under high pressure, cooled to approximately 0* C., is fed to a set of nozzles together with a high-pressure airflow serving as a dispersion agent to convert the issuing fluid into fine droplets which are discharged into a low-pressure airstream of subfreezing temperature. The water is advantageously precharged with ice crystals or other nucleating agents, such as silver iodide, and may also have a surfactant admixed therewith to lower its surface tension.

United States Patent inventors Fritll [56] References Cited a h I K I UNITED STATES PATENTS c 1.437.201 11/1922 Schumann 239/567 kuhnlenz. Deisenhoien. all of. Germany A 1 No 810 7 2.516.401 7/1950 Marcuse 239/424 X M 1969 2.67 .471 4/1954 Pierce. 11 62/121 x e d k' i 3.062.454 11/1962 Cocks 239/4245 x 3.257.815 6/1966 Brocoffet a1.. 62/347 x Ass1gnee Linde Aktkngesellschaft 3 298 612 1/1967 T 62/74 X "olbrkaekkmth' Germ'ny I orrens P A r 8 I968 3.301.485 1/1967 Tropeano et a1... 62/74X 54 3.434.661 3/1969 B6 1 C131. 239/2 3459/68 3.464.625 9/1969 Carlsson .1 239/424 X FOREIGN PATENTS 1.437.437 1/1965 France 239/2 Primary Examiner-Wil1iam E. Wayner AllorneyKarl F. Ross PROCESS AND SYSTEM FOR MAKNG ABSTRACT: Water under high pressure. cooled to approxi- ARTIHCIALSNOW mately 0 C.. is fed to a set of nozzles together with a high- Chum 3 Drum pressure airflow serving as a dispersion agent to convert the is- U.S. Cl 62/347, suing fluid into fine droplets which are discharged into a low- 62/121. 239/2 pressure airstream of subfreezing temperature. The water is Int. Cl. F250 3/02 advantageously precharged with ice crystals or other nucleat- Fleld of Search 2/74. 347. in; agents. such as silver iodide. and may also have a surfactent admixe d therewith to lower its surface tension.

Wll'fl SUIFlfI/IWI' PROCESS AND SYSTEM FOR MAKING ARTIFICIAL SNOW Our present invention relates to a process and a system for making artificial snow.

in conventional systems of this type, large quantities of compressed air are admixed with relatively small amounts of entrained water which, upon subsequent expansion of the mixture into an atmosphere of sufficiently low temperature and high humidity, crystallizes as snow flakes. The successful operation of a snow machine based on this principle is generally possible only at ambient temperatures well below freezing, e.g. less than C., and requires an air compressor of large capacity to deliver a constant flow of compressed air at the rate heretofore considered necessary.

The general object of our present invention is to provide an improved snow machine, based upon a novel process of making artificial snow, which avoids the above drawbacks and which is effective at ambient temperatures just below the freezing mark while being substantially insensitive to variations in relative humidity.

We have found, in accordance with the present invention, that the aforestated object can be realized by allowing a continuous flow of water under high pressure and at a tempera ture close to 0 C. to issue from one or more expansion orifices in the form of small droplets into a low-pressure airstream of subfreezing temperature, Le. a temperature up to about l C.

The expansion 'of the cold water into fine droplets, brought about by a suitable dimensioning of the orifice diameter and by the applied pressure differential, exposes a large effective surface area of the liquid to direct contact with the ambient air, this expansion causing a certain supercooling of the water which. accordingly, readily gives up its latent heat of fusion to the surrounding atmosphere.

The dispersion of the water discharged through the orifices may be intensified by the admixture of a minor proportion of a high-pressure gas of more or less water-insoluble character with the water in a'minor proportion by weight. For the salte of simplicity and economy, this gas is preferably air under a pressure slightly higher than that of the water flow, in a proportion ranging between substantially l and 4 m. STF per m. of water. A particularly advantageous ratio is 3 m. STP of air for each cubic meter of water.

Another adjuvant cspableof promoting the snow formation is a nucieating agent admixed with the water flow in finely comminuted crystalline form. While ice could be used for this purpose it injected into the flow at a location close to the discharge orifices, other compounds of similar crystalline structure (such as silver iodide) are more stable so as to be admixable with the water ahead of the high-pressure pump. The quantity of such nucleating agent should substantially exceed the saturation rate of the water and, in the case of silver iodide, is advantageously on the order of the equivalent of l0" N.

Alternatively, or in addition. a surfactant in powdered or liquid form may be added to the water to reduce its surface tension, thereby facilitating its dispersion into fine droplets. Any commercially available household detergent may he used for this purpose. in the case of a powder, such as an alkylaryl sulfonate, a quantity of about -15 grams per in. of water has been found highly satisfactory; in the case of liquid detergents, such as an ester of polyethylene glycol, a proportion of roughly 100 ml. per m. of water is suitable.

The above and other features of our invention will become more fully apparent hereinafter from the following detailed description given with reference to the accompanying drawing in which:

FlG. 1 illustrates, somewhat diagrammatically and in axial sectional view, the basic structure of a snow machine embodying our invention;

FlG. 2 is a side elevational view, partly in section and on an enlarged scale, ofa nozzle forming part of the machine of FlG. I; and

FIG. .3 is a side elevational view, partly in section, of a modified nozzle-supporting structure forming part of a machine according to the invention.

in FIG. I we have shown a tubular nozzle carrier 35 of cylindrical configuration whose inner bore 37 accommodates an electric fan 36 driven by a motor 41. Fan 36 generates a circulation of air passing axially through the front end 38 of body 35 which carries an annular array of nozzles I with discharge orifices 7 pointing in the direction of the airflow. The nozzles I are connected in parallel, via internal conduits 42, to a manifold 40 in the form of an annular channel to which water is continually supplied under high pressure by a pump 43, followed by a cooler 44, via a pipe 48.

Conduits 42, which represent the inlets to the nozzles I, also communicate via passages 45 with another manifold 39 which is connected to the output end of an air compressor 46 by way of a pipe 49. The delivery pressure of pump 43 may be on the order of 10 atmospheres, with the output pressure of blower 46 slightly higher. More specifically, a water pressure of 6 atmospheres (gauge) has been found adequate with nozzle orifices 7 of 0.7-mm. diameter whereas. for larger orifices, e.g. of 2.3-mm. diameter, correspondingly elevated water pressures on the order of i5 atmospheres (gauge) would be called for.

The restricted passages 45 exert a throttling effect upon the airflow entering the nozzles I from annular channel 39. This throttling effect is desirable to insure a substantially uniform rate of airflow at each nozzle, despite the fact that the several passages 45 are at different distances from the supply line 49.

A similar but less pronounced throttling action is exerted upon the waterflow by the passages 42 linking the nozzles I with the annular channel 40. I

- The circulation of cold atmospheric air past the nozzle orifices 7 creates a Vcnturi effect which helps aspirate the water/air mixture from the nozzles I whereby the water is discharged in the form of small droplets into the airstream. The maximum diameter of these droplets, under the operating conditions specified above. is on the order of 0.l mm. The desired ratio of water to air, within the range previously set forth, can be varied by adjusting the relative speeds of pump 43 and blower 46.

FlG. 2 shows a preferred construction of anyof the nozzles l illustrated schematically in FlG. l. The nozzle I of FIG. 2 has a tubular housing II terminating at its front end in the oriflce 7, housing It being formed with internal threads 47 engsged by mating threads on a tubular insert I5 and on a loclting ring I7. insert I5 defines with the inner front wall of housing It a vortex chamber 16 into which water, with or without admixed air, flows by way of lateral apertures 19 in insert I5 after entering same from the rear through ring I7. The apertures I9 (only one shown) are centered on generally tangentially inclined axes, as is well known per .re, so as to impart to the exiting fluid a swirling motion in its travel toward orifice 7. Male threads I3 on the rear of housing It enable the nozzle 1 to be screwed into a threaded seat in the carrier '35 of FIG. I or in one of two annular carrier members ll, 21 shown in FlG. 3 and described more fully hereinafier; the midportlon 14, of the nozzle housing is formed for this purpose into a polygonal flange engageable by a wrench.

The machine illustrated in FIG. 3 comprises, in addition to the two aforementioned annular nozzle carriers 21 and II, a pair of end caps 22. and I3 threadedly secured to these nozzle carriers which in turn are screwed together so as to form a generally cylindrical body enclosing a fluid chamber 25, the joints between members II, 21', 22, 23 being made fiuidtight by interposed annular gaskets 24. Chamber 25 communicates with an inlet pipe 48 (cf. FIG. 1) through which nearly freezing water at high pressure is supplied from the cooler 44. Each nozzle carrier 21, 21 is part of a tubular shell formed with an annular, array of threaded bores 26, 26 designed to receive the nozzles l of FlG. 2, as particularly illustrated for the carrier 21'. Seats 26 and 26' are provided with longitudinal grooves 28, 28' through which air from an annular channel 3t. 31' can be admitted to the corresponding nozzle inlet by way of an injection passage 29. 29 including a throttling valve 30,

I constriction of the injection passage or by a porous insert of,

say, sintered ceramic material. The water from space 25 reaches the nozzles through conduits 27, 27' terminating at the seats 26, 26'. Air inlets 49, 49', originating at the blower 46 of FIG. 1, terminate at the annular manifolds 31 and 31'.

In the operation of the assembly ofFlG. 3, air from a lowpressure fan or the like (or simply atmospheric air if the device is exposed to the wind) moves again past the orifices of nozzles l to help induce the discharge of line droplets of water which, especially if changed with a nucleating agent and/or a surfactant as described above, crystallize upon contact with the atmosphere so as to turn into snow flakes.

We claim:

1, A system for making artificial snow, comprising an array of nozzles provided with dispersion orifices and conduits lead ing to said orifices, said array being centered on an axis. pump means for supplying water at high pressure to said nozzles by way of said conduits, cooling means between said pump means and said nozzles for maintaining the temperature of the water at said orifices at substantially C., injection means terminating at said conduits for admixing a stream of compressed gas with said water ahead of said orifices, throttle means in said injection means for reducing the fiow rate of said gas to a minor proportion by weight of the flow rate of the water, said orifices opening into an air space of substantially atmospheric pres sure and subfreezing temperature, and circulation means in said air space for propelling the air therein past said orifices in the direction of said axis.

2. A system as defined in claim 1 wherein said gas is air, said injection means comprising a common manifold connected with said conduits and a source of high-pressure air discharg ing into said manifold.

3. A system as defined in claim 1, further comprising a generally cylindrical carrier having said nozzles peripherally disposed thereon, said carrier being provided with an annular channel constituting said manifold, said air injection means forming passages in said carrier between said channel and said nozzles.

4. A system as defined in claim 3 wherein said carrier has seats for said noules provided with inlets for water from said cooling means, said nozzles being open toward said seats for receiving the water therefrom.

5. A system as defined in claim 4 wherein said carrier forms part of a shell subdivided into a plurality of axially adjoining,

detachably interconnected carriers construction each with a set of said dividual thereto.

6. A system as defined in claim 5 wherein said shell surrounds a water chamber connected to said pump means through said cooling means. said inlets extending outwardly through said shell from said chamber.

7. A system as defined in claim I wherein said orifices have diameters in a range between substantially 0.5 mm. and 2.5 mm.

8. A system for making artificial snow, comprising a generally cylindrical carrier, an array of nozzles provided with of substantially identical nozzles and a manifold in- 00 ing at said conduits for admixing a stream of compressed gas with said water ahead of said orifices, and throttle means in said injection means for reducing the flow rate of said gas to a minor proportion by weight of the flow rate of the water, said orifices opening into an air space of substantially atmospheric pressure and subfreezing temperature, said carrier being provided with an annular channel constituting a common manifold connected with said conduits, and a source of highpressure air discharging into said manifold, said air injection means forming passages in said carrier between said channel and said nozzles.

9. A system as defined in claim 8 wherein said carrier has seats for said nozzles provided with inlets for water from said cooling means, said nozzles being open toward said seats for receiving the water therefrom.

10.-A system as defined in claim 8 wherein said orifices have diameters in a range between substantially 0.5 mm. and 2.5 mm.

11. A system as defined in claim 8 wherein said carrier forms part of a shell surrounding a water chamber connected to said pump means through said cooling means, said inlets extending outwardly through said shell from said chamber.

12. A system as defined in claim 8 wherein said carrier forms part of a shell subdivided into a plurality of axially adjoining, detachably interconnected carriers of substantially identical construction each with a set of said nozzles and a manifold individual thereto. 

1. A system for making artificial snow, comprising an array of nozzles provided with dispersion orifices and conduits leading to said orifices, said array being centered on an axis, pump means for supplying water at high pressure to said nozzles by way of said conduits, cooling means between said pump means and said nozzles for maintaining the temperature of the water at said orifices at substantially 0* C., injection means terminating at said conduits for admixing a stream of compressed gas with said water ahead of said orifices, throttle means in said injection means for reducing the flow rate of said gas to a minor proportion by weight of the flow rate of the water, said orifices opening into an air space of substantially atmospheric pressure and subfreezing temperature, and circulation means in said air space for propelling the air therein past said orifices in the direction of said axis.
 2. A system as defined in claim 1 wherein said gas is air, said injection means comprising a common manifold connected with said conduits and a source of high-pressure air discharging into said manifold.
 3. A system as defined in claim 1, further comprising a generally cylindrical carrier having said nozzles peripherally disposed theReon, said carrier being provided with an annular channel constituting said manifold, said air injection means forming passages in said carrier between said channel and said nozzles.
 4. A system as defined in claim 3 wherein said carrier has seats for said nozzles provided with inlets for water from said cooling means, said nozzles being open toward said seats for receiving the water therefrom.
 5. A system as defined in claim 4 wherein said carrier forms part of a shell subdivided into a plurality of axially adjoining, detachably interconnected carriers of substantially identical construction each with a set of said nozzles and a manifold individual thereto.
 6. A system as defined in claim 5 wherein said shell surrounds a water chamber connected to said pump means through said cooling means, said inlets extending outwardly through said shell from said chamber.
 7. A system as defined in claim 1 wherein said orifices have diameters in a range between substantially 0.5 mm. and 2.5 mm.
 8. A system for making artificial snow, comprising a generally cylindrical carrier, an array of nozzles provided with dispersion orifices and conduits leading to said orifices, said nozzles being peripherally disposed on said carrier, pump means for supplying water at high pressure to said nozzles by way of said conduits, cooling means between said pump means and said nozzles for maintaining the temperature of the water at said orifices at substantially 0* C., injection means terminating at said conduits for admixing a stream of compressed gas with said water ahead of said orifices, and throttle means in said injection means for reducing the flow rate of said gas to a minor proportion by weight of the flow rate of the water, said orifices opening into an air space of substantially atmospheric pressure and subfreezing temperature, said carrier being provided with an annular channel constituting a common manifold connected with said conduits, and a source of high-pressure air discharging into said manifold, said air injection means forming passages in said carrier between said channel and said nozzles.
 9. A system as defined in claim 8 wherein said carrier has seats for said nozzles provided with inlets for water from said cooling means, said nozzles being open toward said seats for receiving the water therefrom.
 10. A system as defined in claim 8 wherein said orifices have diameters in a range between substantially 0.5 mm. and 2.5 mm.
 11. A system as defined in claim 8 wherein said carrier forms part of a shell surrounding a water chamber connected to said pump means through said cooling means, said inlets extending outwardly through said shell from said chamber.
 12. A system as defined in claim 8 wherein said carrier forms part of a shell subdivided into a plurality of axially adjoining, detachably interconnected carriers of substantially identical construction each with a set of said nozzles and a manifold individual thereto. 